Garbled characters appear when exporting queried data as a csv file in Java

1. Problem

When the queried data is exported as an xls file (UTF-8 encoding), the data is normal; but when it is exported as a CSV file, the Chinese garbled characters are also encoded in UTF-8. When exported in GBK encoding, the Chinese display is normal.

I thought the problem was solved. When I exported data containing Latin characters (such as ÀÆÊàÌ) later, the data was displayed normally when exported as an xls file. When exported as a CSV file, the Latin characters in the file were displayed as "?".

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2. Solution

The file exported in CSV mode does not contain BOM information by default. This problem can be solved by setting the BOM identifier (byte stream starting with EF BB BF) for the content to be output.

The specific method is as follows:

...
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(response.getOutputStream(), "UTF-8");  
// 要输出的内容  
result = (String)contentMap.get(RESPONSE_RESULT);  
response.setHeader("Content-Disposition", "attachment;filename=test.csv");  
outputStreamWriter.write(new String(new byte[]{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF}));  
outputStreamWriter.write(result);  
outputStreamWriter.flush();

If it is implemented by OutputStream stream, the parameters can be modified as follows:

out = response.getOutputStream();     
//加上UTF-8文件的标识字符      
out.write(new byte []{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF});

Note:

BOM: Byte Order Mark, byte order mark (the following is taken from Baidu Encyclopedia)

In UCS encoding, there is one called "Zero Width No-Break Space", the Chinese translation is "Zero Width No-Break Space" character, its encoding is FEFF. FFFE is a character that does not exist in UCS, so it should not appear in actual transmission.

The UCS specification recommends that we transmit the characters "Zero Width No-Break Space" before transmitting the byte stream, so that if the receiver receives FEFF, it means that the byte stream is Big-Endian; if Receiving FFFE indicates that the byte stream is Little-Endian.

So the character "Zero Width No-Break Space (Zero Width No-Break Space)" is also called BOM.

UTF-8 does not require a BOM to indicate the byte order, but you can use a BOM to indicate the encoding method. The UTF-8 encoding for the character "Zero Width No-Break Space" is EF BB BF. So if the receiver receives a byte stream starting with EF BB BF, it knows that it is UTF-8 encoded.

Windows uses BOM to mark the encoding method of text files.

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